Novel Inducers of Gliotoxin Production In Aspergillus Fumigatus

<p>Secondary metabolites are produced by numerous organisms and can either be benign to humans or harmful. Genes involved in the synthesis and transport of these secondary metabolites are frequently found in gene clusters, which are often located in subtelomeric regions of the chromosome. These clusters are often coordinately regulated, being almost exclusively dependent on transcription factors that are located within the clusters themselves. Secondary metabolites are also regulated by a variety of factors, including nutritional factors, environmental factors and developmental processes. Gliotoxin, which is produced by a variety of <em>Aspergillus</em> species, <em>Trichoderma</em> species, and <em>Penicillium</em> species, exhibits immunosuppressive properties and has therefore been the subject of research for many laboratories. There have been a few proteins shown to regulate the gliotoxin cluster, most notably GliZ, a Zn₂Cys₆ binuclear finger transcription factor that lies within the cluster, and LaeA, a putative methyltransferase that globally regulates secondary metabolism clusters within numerous fungal organisms, although no study has demonstrated the direct binding of any protein to a promoter region in the gliotoxin cluster.</p> <p>I report here two novel proteins, GipA, a C₂H₂ transcription factor and GipB, a hybrid sensor kinase, which are involved in regulating the gliotoxin biosynthetic cluster. GipA plays an important role in gliotoxin production, as high-copy expression of <em>gipA</em> induces gliotoxin biosynthesis and loss of <em>gipA</em> reduces gliotoxin biosynthesis by 50%. GipB is also involved in regulating gliotoxin production, as high-copy expression of <em>gipB</em> induces gliotoxin biosynthesis, but only during certain stages of asexual development. Furthermore, loss of <em>gipB</em> reduces gliotoxin biosynthesis by 10%. Based on data obtained from this project, I propose a model for the regulation of <em>gliA</em>, the efflux pump of the gliotoxin cluster, which involves GipB signaling through both GliZ and GipA. I propose that GliZ and GipA are interdependent, as mutation of the GipA DNA binding site in the <em>gliA</em> promoter negatively affects both GliZ-mediated and GipA-mediated induction of <em>gliA</em>. This is further supported by the fact that GliZ cannot fully induce <em>gliA</em> in the absence of GipA and vice versa. This is the first time that anyone has shown evidence of a protein directly binding to the gliotoxin cluster. Even though biosynthetic clusters are often coordinately regulated, my model raises the possibility that <em>gliA</em> is independently regulated, as the layout of the binding site in the <em>gliA</em> promoter is not present upstream of any other genes in the gliotoxin cluster, except for <em>gliZ</em>.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2013

Author dc:creator

• Schoberle, Taylor J

Contributors dc:contributor

• Dr. Gregory May
• Dr. Michelle Barton
• Dr. Kevin Morano

• Gliotoxin
• Gene Transcription
• Fungal genetics
• Fungi
• Genetic Processes
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/379

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1413